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Comparison of Two Methods of Obtaining Digital Orthodontic Models: Direct vs. Indirect

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Technical Report

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Uniformed Services University Of The Health Sciences Bethesda United States

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Introduction Advancements in the application of technology have been progressing at an unprecedented rate in the field of orthodontics. One area in which technologies are constantly evolving is in the production of digital orthodontic models for both treatment planning purposes as well as the fabrication of orthodontic appliances. The purpose of this study is to compare linear measurement accuracy on three-dimensional digital orthodontic models obtained by direct scanning to those obtained by indirect scanning. Methods A resin model with reproducible occlusion was fabricated and used as the control. Three dimensional digital orthodontic models were produced both by direct scanning of the control model and indirect scanning using a PVS impression and bite registration. Inter-arch and intra-arch linear measurements were made. The percent change from the control model for each scanning method was evaluated. Results Analysis revealed a statistically significant difference in linear measurement accuracy for both scanning methods when compared to the original model control. Overall, the iTero iOC direct scan was found to be more accurate and reliable than the ESM R700 indirect scan. Three of the five inter-arch measurements were found to be significantly more accurate and displayed asmaller standard deviation at every measurement location. Also, it was found that the intra-arch measurements tended to be more accurate and reliable for both scanning methods. Conclusions The larger inter-arch differences were most likely due to inaccuracies in the digital articulation of the models using the bite registration material when utilizing the indirect method. In conclusion, the larger in accuracies are most likely not clinically significant. This study suggests that digital models produced by direct scanning are more accurate for not only diagnosis and treatment planning but fabrication of orthodontic appliances.

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